Tail control system of a biomimetic ornithopter and control method thereof

Abstract

The application is suitable for the field of bionic flapping-wing aircraft technology, and provides a tail wing control system of a bionic flapping-wing aircraft and a control method thereof.The tail wing control system comprises a fuselage module, a tail wing actuating mechanism, two groups of SMA driving modules, and a control and communication module.The tail wing actuating mechanism is assembled at the tail of the fuselage module and comprises a horizontal tail, a vertical tail and a fixed rod.Each group of the SMA driving modules is embedded in the fuselage module and comprises an SMA wire, a spring and a pulley transmission mechanism.The one end of the SMA wire is fixedly connected with the fuselage module, the other end of the SMA wire is connected with the spring through the pulley transmission mechanism, the other end of the spring is fixedly connected with the fuselage module, and the pulley transmission mechanism comprises a moving rod and a pulley.The SMA driving module is electrically connected with the control and communication module.The application can realize accurate control of the tail rudder angle under the premise of maintaining light weight, and improve the attitude adjustment capability and flight stability of the aircraft.

Description

Technical Field

[0001] This invention relates to the field of biomimetic flapping-wing aircraft technology, and more specifically, to a tail control system and control method for a biomimetic flapping-wing aircraft. Background Technology

[0002] Miniature biomimetic flapping-wing aircraft, due to their small size, light weight, and high maneuverability, have broad application prospects in fields such as complex terrain reconnaissance, environmental monitoring, and target tracking. The tail fin, as a key component for attitude control in flapping-wing aircraft, directly determines the pitch and yaw stability of the aircraft through its control precision.

[0003] Traditional flapping-wing aircraft typically employ micro servo motors for tail control, directly deflecting the tail control surfaces. However, these micro servos are relatively heavy, resulting in a significant weight proportion for micro flapping-wing aircraft and severely compressing the payload space. Furthermore, traditional servo control schemes are complex in structure, consume high power, and struggle to achieve continuous and smooth angle adjustments, failing to meet the comprehensive requirements of micro flapping-wing aircraft for lightweight, low-power, and high-precision control.

[0004] In recent years, shape memory alloy (SMA), as a novel smart material, has attracted widespread attention in the field of biomimetic robotics due to its advantages such as high power-to-weight ratio, simple structure, and noiselessness. However, the application of SMA in the tail control of flapping-wing aircraft still faces two major technical challenges: first, the phase transition process of SMA exhibits significant nonlinearity and hysteresis characteristics, making it difficult to achieve precise angle adjustment through open-loop control; second, the resistance of SMA changes with temperature, but existing solutions have failed to effectively utilize this self-sensing characteristic for closed-loop control. Therefore, it is urgent to design a tail control system that can overcome the nonlinearity of SMA and achieve precise closed-loop control. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide a tail control system and control method for a biomimetic flapping-wing aircraft.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a tail control system for a biomimetic flapping-wing aircraft, comprising: The fuselage module adopts a lightweight structure and has an internal mounting slot; A tail fin actuator is mounted on the tail of the fuselage module. The tail fin actuator includes a horizontal tail rudder, a vertical tail rudder, and a fixed rod. The fixed rod includes a first fixed rod and a second fixed rod. The first fixed rod is fixedly connected to the horizontal tail rudder, and the second fixed rod is fixedly connected to the vertical tail rudder. Two sets of SMA drive modules are embedded inside the fuselage module. Each SMA drive module includes an SMA wire, a spring, and a pulley transmission mechanism. One end of the SMA wire is fixedly connected to the fuselage module, and the other end of the SMA wire passes around the pulley transmission mechanism and connects to the spring. The other end of the spring is fixedly connected to the fuselage module. The pulley transmission mechanism includes a moving rod and a pulley. The pulley can rotate around an axis. One end of the moving rod is fixed to the pulley and rotates synchronously with it. The other end of the moving rod is connected to one of the fixed rods in the corresponding tail fin actuator. A control and communication module, which is electrically connected to the SMA drive module.

[0007] The present invention is further configured such that: the SMA wire is made of nickel-titanium shape memory alloy material, which produces axial shrinkage when heated to above the austenitic phase transformation temperature, with a maximum shrinkage strain of 3%-4%.

[0008] The present invention is further configured such that the length of the fixed rod of the tail fin actuator is equal to the length of the moving rod.

[0009] The present invention is further configured such that: the radius r of the pulley and the length l of the SMA wire satisfy the following relationship: ; in, The length of SMA yarn after heat shrinkage. The initial length of the SMA filament. This represents the rotation angle of the pulley.

[0010] The present invention is further configured such that: the control and communication module includes a multi-physics coupling control unit and a wireless communication unit, the multi-physics coupling control unit is signal-connected to a microcontroller, the microcontroller controls the heating current of the SMA wire through a PWM signal, and the wireless communication unit is electrically connected to the microcontroller.

[0011] The present invention is further configured such that the multiphysics coupling control unit incorporates an SMA wire multiphysics coupling model, which includes: The electrothermal drive sub-model describes the relationship between the SMA wire temperature T and the driving voltage U and time t. When the SMA wire is energized and heated, the change in SMA wire temperature T satisfies the following: ; Where T is the temperature of the SMA filament. Where is the ambient temperature, h is the convective heat transfer coefficient, R is the resistance of the SMA wire, A is the heat dissipation surface area, U is the driving voltage of the SMA wire, m is the mass, C is the specific heat capacity, and t is the time. Phase transformation kinetics sub-model: describes the relationship between martensite volume fraction ξ and temperature T and stress σ, and the volume fraction of detwinned martensite during heating. satisfy: ; in, To determine the volume fraction of twinned martensite, , Here, σ represents the start and end temperatures of the austenitic phase transformation, and σ represents the stress. The equivalent conversion factor for austenitic phase transformation stress; Resistance-strain quantum model: describing the relationship between the resistance R and strain of an SMA wire The relationship between the SMA wire resistance and the resistance can be expressed as: ; in, , ξ represents the resistivity of the martensitic phase and the austenitic phase, respectively; ξ represents the volume fraction of martensite; l represents the length of the SMA wire; and S represents the cross-sectional area. strain The martensite volume fraction ξ satisfies: ; in, The real-time strain of the SMA wire. and These are the martensitic elastic modulus and the austenitic elastic modulus, respectively. Strain-Angle Sub-model: Describes the tail rudder deflection angle Strain of SMA wire The relationship between the tail rudder deflection angle satisfy: ; in, For the tail rudder deflection angle, The real-time strain of the SMA wire. To maximize recoverable strain, This is the maximum deflection angle.

[0012] The present invention is further configured such that the multiphysics coupling control unit has two built-in control modes: Step control mode: The PWM duty cycle is increased or decreased in fixed steps of 1%-5% to achieve step adjustment of the tail rudder angle; Direct control mode: Based on the target tail rudder angle, the required PWM duty cycle is calculated by back-calculating through a multiphysics coupling model, and the tail rudder is directly driven to deflect to the target position.

[0013] The present invention is further configured such that, based on the target tail rudder angle, the required PWM duty cycle is specifically calculated using the multiphysics coupling model: Based on the target tail rudder angle, the effective voltage U required to drive the SMA wire (31) is calculated using the multiphysics coupling model. Based on the relationship between the effective voltage U and the PWM duty cycle The required PWM duty cycle is calculated, where U is the effective voltage. Where is the power supply voltage, and D is the PWM duty cycle.

[0014] A tail control method for a biomimetic flapping-wing aircraft, using a tail control system for a biomimetic flapping-wing aircraft as described above, includes the following steps: S1. The wireless communication unit receives external control commands and obtains the target tail rudder angle; S2. The microcontroller calculates the theoretical PWM duty cycle required to achieve the target tail rudder angle based on the multiphysics coupling model. The S3 and SMA wire drive circuits output PWM signals with corresponding duty cycles to drive the SMA wires to heat up and generate contraction displacement, and the pulley transmission mechanism drives the tail rudder to deflect. S4. The microcontroller back-calculates the current strain of the SMA wire based on the resistance-strain sub-model, and then calculates the actual deflection angle of the tail rudder using the strain-angle sub-model. S5. Compare the actual tail rudder deflection angle with the target tail rudder angle. If the deviation exceeds the set threshold, adjust the PWM duty cycle according to the deviation to achieve closed-loop control. S6. Repeat steps S3-S5 until the tail rudder deflects to the target tail rudder angle and remains stable.

[0015] Compared with existing technologies, the beneficial effects achieved by this invention are as follows: This invention adjusts the heating duty cycle of the SMA filament using a PWM signal to control the temperature and phase transformation degree of the SMA filament, and then drives the tail rudder to the target tail rudder angle through a pulley transmission mechanism. During heating, the SMA filament undergoes a reverse phase transformation from martensite to austenite, resulting in contraction displacement that drives the pulley to rotate. During cooling, it returns to its original position under the action of a spring, achieving bidirectional reciprocating deflection of the tail rudder. This allows for precise control of the tail rudder angle while maintaining lightweight design, thereby improving the aircraft's attitude adjustment capabilities and flight stability. This invention enables precise control of the tail rudder angle while maintaining lightweight design, improving the aircraft's attitude adjustment capabilities and flight stability. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the overall structure of the present invention; Figure 2 This is a schematic diagram of the SMA driver module in this invention; Figure 3 This is a schematic diagram showing the connection between the horizontal tail rudder and the SMA drive module in this invention; Figure 4 This is a schematic diagram showing the connection between the vertical tail rudder and the SMA drive module in this invention. Figure 5 This is a schematic diagram of the circuit principle of the SMA driver module in this invention; Figure 6 This is a schematic diagram of the circuit principle of the multiphysics coupling control unit in this invention; Figure 7 This is a schematic diagram of the temperature rise curves of the SMA wire under different voltages in this invention; Figure 8 This is a schematic diagram showing the relationship between the volume fraction of SMA martensite and temperature under different stresses in this invention. Figure 9 This is a schematic diagram of the relationship between input voltage and deflection angle in this invention; Figure 10 This is a schematic diagram of the circuit principle of the wireless communication unit in this invention; Figure 11 This is a schematic diagram of the method flow of the present invention.

[0017] Explanation of reference numerals in the attached drawings: 1. Fuselage module; 2. Tail fin actuator; 21. Horizontal tail rudder; 22. Vertical tail rudder; 23. Fixed rod; 231. First fixed rod; 232. Second fixed rod; 3. SMA drive module; 31. SMA wire; 32. Spring; 33. Pulley transmission mechanism; 331. Moving rod; 332. Pulley; 4. Control and communication module; 41. Multiphysics coupling control unit; 42. Wireless communication unit. Detailed Implementation

[0018] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0019] It should be noted that, unless otherwise specified, all technical and scientific terms used in this application have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains.

[0020] Please see Figures 1 to 11 The present invention provides the following technical solutions: Example 1, see Figures 1 to 10 A tail control system for a biomimetic flapping-wing aircraft, comprising: The fuselage module 1 adopts a lightweight structure and has an internal mounting slot for assembling the SMA drive module 3 and the control and communication module 4. Tail wing actuator 2 is mounted on the tail of fuselage module 1. Tail wing actuator 2 includes horizontal tail rudder 21, vertical tail rudder 22 and fixed rod 23. Fixed rod 23 includes first fixed rod 231 and second fixed rod 232. First fixed rod 231 is fixedly connected to horizontal tail rudder 21 and second fixed rod 232 is fixedly connected to vertical tail rudder 22. Two sets of SMA drive modules 3 are embedded inside the body module 1. Each set of SMA drive modules 3 includes an SMA wire 31, a spring 32 and a pulley transmission mechanism 33. The SMA drive module 3 is electrically connected to the control and communication module 4. The control and communication module 4 is used to receive external control commands, control the tail rudder, and provide feedback on the tail rudder status.

[0021] See Figure 2 The specific structure of the SMA drive module 3 is as follows: one end of the SMA wire 31 is fixedly connected to the body module 1, and the other end of the SMA wire 31 passes around the pulley transmission mechanism 33 and connects to the spring 32. The other end of the spring 32 is fixedly connected to the body module 1.

[0022] Specifically, the pulley transmission mechanism 33 includes a moving rod 331 and a pulley 332. The pulley 332 can rotate around an axis, and the moving rod 331 is fixed on the pulley 332 and rotates synchronously with it. When the SMA wire 31 is heated, it undergoes a reverse phase transformation from martensite to austenite, generating an axial contraction displacement that drives the pulley 332 to rotate. When cooled, it resets under the action of the bias spring 32, realizing the bidirectional reciprocating deflection of the tail rudder.

[0023] See Figures 3 to 4 The connection relationship between the pulley transmission mechanism 33 and the tail rudder is as follows: the first fixed rod 231 is fixedly connected to the horizontal tail rudder 21, and the second fixed rod 232 is fixedly connected to the vertical tail rudder 22. The first fixed rod 231 and the second fixed rod 232 are connected to the end of the moving rod 331 of their respective pulley transmission mechanism 33 through a connecting shaft.

[0024] It is important to note that, to ensure consistent output angles, the length of the fixed rod 23 must be equal to the length of the movable rod 331. When the pulley 332 rotates by an angle... At the same time, the movable rod 331 rotates by the same angle, which drives the fixed rod 23 to rotate through the connecting shaft, thereby driving the tail rudder to deflect by an angle. ,satisfy .

[0025] Specifically, SMA wire 31 has a diameter of 0.2-0.3 mm and a length of 40-60 mm. It is made of nickel-titanium shape memory alloy material and produces axial shrinkage when heated above the austenitic phase transformation temperature, with a maximum shrinkage strain of 3%-4%.

[0026] Furthermore, the radius r of pulley 332 and the length l of SMA wire 31 satisfy the following relationship: ; in, The length of SMA yarn 31 after heat shrinkage. This is the initial length of SMA wire 31. Let be the rotation angle of pulley 332.

[0027] See Figure 5 The circuit principle of SMA drive module 3 is as follows: Two IRLML6244s are used as high-speed electronic switches to control the drive chips of the horizontal tail rudder 21 and the vertical tail rudder 22 respectively. One end of the SMA wire 31 is connected to the output of the regulated power supply (3.3V), and the other end is connected to the drain of the MOSFET (MOSFET Switch Circuit, a voltage-controlled device with three terminals: gate, drain, and source. The gate voltage controls the formation and disappearance of the conductive channel between the source and drain to achieve the switching function). The gate of the MOSFET is connected to the drive signal output by the STM32, and the source is grounded. When the drive signal is high, the MOSFET is turned on, a current loop is formed, and the SMA wire 31 is heated; when the drive signal is low, the MOSFET is turned off, the current loop is broken, and the SMA wire 31 stops heating.

[0028] When a PWM signal (Pulse width modulation) is used as the driving signal, the high-frequency switching of the signal can control the high-frequency switching of the MOSFET, that is, the voltage across the SMA wire 31 switches between 0V and 3.3V at high frequency, thereby achieving safe heating.

[0029] PWM duty cycle refers to the proportion of the high-level duration within a pulse cycle to the entire cycle time. By adjusting the PWM duty cycle, the effective voltage applied to the SMA wire 31 can be controlled. Where D is the duty cycle. This is the power supply voltage.

[0030] Specifically, the frequency of the PWM signal is 10-50Hz, with the most preferred frequency being 20Hz. That is, the duty cycle adjustment range of the PWM signal is 10%-90%, where 10%-30% corresponds to the initial stage of phase transition of SMA wire 31, 30%-60% corresponds to the main phase transition stage, and 60%-90% corresponds to the phase transition saturation stage.

[0031] Furthermore, the control and communication module 4 includes a multi-physics coupling control unit 41 and a wireless communication unit 42. The multi-physics coupling control unit 41 is signal-connected to a microcontroller. The microcontroller controls the heating current of the SMA wire 31 through a PWM signal. The wireless communication unit 42 is electrically connected to the microcontroller and is used to receive external control commands and provide feedback on the tail rudder status.

[0032] See Figure 6 The circuit principle of the multi-physics coupling control unit 41 is as follows: a single-chip microcomputer minimum system is used as the main control circuit. To facilitate wiring and debugging, the chip pins are led out as solder points through P1 and P2. At the digital power supply, three 100nF capacitors are connected in parallel between the power signal and ground to form a decoupling network to suppress power ripple and high-frequency noise. For the analog power supply VDDA, an inductor is connected in series with a filter capacitor to achieve digital power supply isolation. In addition, using the SWDIO download method, BOOT0 and BOOT1 are directly pulled down to ground through resistors. Preferably, an STM32F103C8T6 microprocessor is used, and an IRLML6244 MOSFET is used as the electronic switch.

[0033] Furthermore, the multiphysics coupling control unit 41 incorporates a multiphysics coupling model of the SMA wire 31, which includes the following sub-models: (1) Electrothermal drive sub-model: describes the relationship between the temperature T of SMA wire 31 and the driving voltage U and time t. When SMA wire 31 is energized and heated, the temperature T of SMA wire 31 changes according to the following: ; Where T is the temperature of SMA wire 31. Where is the ambient temperature, h is the convective heat transfer coefficient, R is the resistance of SMA wire 31, A is the heat dissipation surface area, U is the driving voltage of SMA wire 31, m is the mass, C is the specific heat capacity, and t is the time. (2) Phase transformation kinetics sub-model: describes the relationship between martensite volume fraction ξ and temperature T and stress σ. During the heating process, the volume fraction of detwinized martensite... satisfy: ; in, To determine the volume fraction of twinned martensite, , Here, σ represents the start and end temperatures of the austenitic phase transformation, and σ represents the stress. The equivalent conversion factor for austenitic phase transformation stress; (3) Resistance-strain quantum model: describes the relationship between the resistance R and strain of SMA wire 31. The resistance R of SMA wire 31 can be expressed as: ; in, , ξ represents the resistivity of the martensitic and austenitic phases, respectively; ξ represents the volume fraction of martensite; l represents the length of SMA wire 31; and S represents the cross-sectional area. Furthermore, strain The martensite volume fraction ξ satisfies: ; in, For the real-time strain of SMA wire 31, and These are the martensitic elastic modulus and the austenitic elastic modulus, respectively. (4) Strain-angle sub-model: describes the tail rudder deflection angle Strain of SMA wire 31 The relationship between the tail rudder deflection angle satisfy: ; in, For the tail rudder deflection angle, For the real-time strain of SMA wire 31, To maximize recoverable strain, This is the maximum deflection angle.

[0034] Specifically, see Figures 7 to 9 Temperature rise characteristics of SMA wire 31 under different voltages, such as Figure 7 As shown, with increasing voltage, the temperature rise rate of SMA wire 31 increases significantly, and the steady-state temperature also increases significantly. The relationship between the martensite volume fraction of SMA wire 31 and temperature is as follows: Figure 8 As shown, the heating and cooling curves do not coincide, forming a significant hysteresis loop. The relationship between input voltage and output angle is as follows: Figure 9 As shown, due to the hysteresis characteristics of SMA, there is a deviation in the output angle corresponding to the boost and buck processes.

[0035] Furthermore, the multiphysics coupling control unit 41 has two built-in control modes, including a step control mode and a direct control mode, specifically: In step control mode, the PWM duty cycle is increased or decreased in fixed steps of 1%-5% to achieve step adjustment of the tail rudder angle. In direct control mode, the required PWM duty cycle is calculated by using a multiphysics coupling model based on the target tail rudder angle, and the tail rudder is directly driven to deflect to the target position. The two modes can be switched via external commands.

[0036] Furthermore, based on the target tail rudder angle, the required PWM duty cycle is specifically calculated using a multiphysics coupling model: Based on the target tail rudder angle, the effective voltage U required to drive the SMA wire (31) is calculated using a multiphysics coupling model; Based on the relationship between effective voltage U and PWM duty cycle The required PWM duty cycle is calculated, where U is the effective voltage. Where is the power supply voltage, and D is the PWM duty cycle.

[0037] Furthermore, the microcontroller has a built-in hysteresis compensation lookup table, which stores the PWM duty cycle values ​​corresponding to different tail rudder deflection angles during the heating and cooling processes. When a change in tail rudder deflection direction is detected, the microcontroller switches to the corresponding duty cycle-angle mapping relationship according to the hysteresis compensation lookup table.

[0038] See Figure 10 The wireless communication unit 42 uses a DX-BT24-T Bluetooth module (containing two pins, UART_RX and UART_TX, for receiving and transmitting data), which follows the Bluetooth BLE 5.1 ​​protocol. It selects the USART1 of the STM32 chip (USART1 is the serial communication module on the STM32 chip, using two pins, PA9(TX) and PA10(RX), for receiving and transmitting data) to communicate with it. Specifically, the PA9(TX) of the STM32 chip is connected to the UART_RX of the DX-BT24-T Bluetooth module, and the PA10(RX) is connected to the UART_TX of the DX-BT24-T Bluetooth module. The wireless communication unit 42 is used to receive external control commands and provide feedback on the tail rudder status.

[0039] Example 2, see Figure 11 A tail control method for a biomimetic flapping-wing aircraft, using the aforementioned tail control system for a biomimetic flapping-wing aircraft, includes the following steps: S1. Wireless communication unit 42 receives external control commands and analyzes the target tail rudder angle; S2. The microcontroller calculates the theoretical PWM duty cycle required to achieve the target tail rudder angle based on the multiphysics coupling model. The S3 and SMA wire 31 drive circuits output PWM signals with corresponding duty cycles to drive the SMA wire 31 to heat up and generate a contraction displacement, which drives the tail rudder to deflect through the pulley transmission mechanism 33. S4. The microcontroller back-calculates the current strain of SMA wire 31 based on the resistance-strain sub-model, and then calculates the actual deflection angle of the tail rudder using the strain-angle sub-model. S5. Compare the actual tail rudder deflection angle with the target tail rudder angle. If the deviation exceeds the set threshold, adjust the PWM duty cycle according to the deviation to achieve closed-loop control. S6. Repeat steps S3-S5 until the tail rudder deflects to the target tail rudder angle and remains stable.

[0040] Obviously, the embodiments described above are merely some, not all, embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort should fall within the scope of protection of the present invention.

Claims

1. A tail control system for a biomimetic flapping-wing aircraft, characterized in that, include: The fuselage module (1) adopts a lightweight structure and has an internal mounting slot; Tail wing actuator (2), the tail wing actuator (2) is mounted on the tail of the fuselage module (1), the tail wing actuator (2) includes a horizontal tail rudder (21), a vertical tail rudder (22) and a fixed rod (23), the fixed rod (23) includes a first fixed rod (231) and a second fixed rod (232), the first fixed rod (231) is fixedly connected to the horizontal tail rudder (21), and the second fixed rod (232) is fixedly connected to the vertical tail rudder (22); Two sets of SMA drive modules (3) are embedded inside the fuselage module (1). Each set of SMA drive modules (3) includes an SMA wire (31), a spring (32), and a pulley transmission mechanism (33). One end of the SMA wire (31) is fixedly connected to the fuselage module (1), and the other end of the SMA wire (31) passes around the pulley transmission mechanism (33) and connects to the spring (32). The other end of the spring (32) is fixedly connected to the fuselage module (1). The pulley transmission mechanism (33) includes a moving rod (331) and a pulley (332). The pulley (332) can rotate around an axis. One end of the moving rod (331) is fixed on the pulley (332) and rotates synchronously with it. The other end of the moving rod (331) is connected to one of the fixed rods (23) in the corresponding tail fin actuator (2). Control and communication module (4), which is electrically connected to the SMA drive module (3).

2. The tail control system of a biomimetic flapping-wing aircraft according to claim 1, characterized in that: The SMA wire (31) is made of nickel-titanium shape memory alloy material, which produces axial shrinkage when heated above the austenitic phase transformation temperature, with a maximum shrinkage strain of 3%-4%.

3. The tail control system of a biomimetic flapping-wing aircraft according to claim 2, characterized in that, The length of the fixed rod (23) of the tail fin actuator (2) is equal to the length of the moving rod (331).

4. The tail control system of a biomimetic flapping-wing aircraft according to claim 3, characterized in that, The radius r of the pulley (332) and the length of the SMA wire (31) Satisfying Relationship: ； in, The length of the SMA filament (31) after heat shrinkage. The initial length of the SMA filament (31) is given. Let be the rotation angle of pulley (332).

5. The tail control system of a biomimetic flapping-wing aircraft according to claim 4, characterized in that: The control and communication module (4) includes a multi-physics coupling control unit (41) and a wireless communication unit (42). The multi-physics coupling control unit (41) is connected to a micro controller. The micro controller controls the heating current of the SMA wire (31) through a PWM signal. The wireless communication unit (42) is electrically connected to the micro controller.

6. The tail control system of a biomimetic flapping-wing aircraft according to claim 5, characterized in that: The multiphysics coupling control unit (41) incorporates the multiphysics coupling model of the SMA wire (31), which includes: Electrothermal drive sub-model: describes the relationship between the temperature T of the SMA wire (31) and the driving voltage U and time t. When the SMA wire (31) is energized for heating, the temperature T of the SMA wire (31) changes in accordance with the following: ； Where T is the temperature of the SMA filament (31), Where is the ambient temperature, h is the convective heat transfer coefficient, R is the resistance of the SMA wire (31), A is the heat dissipation surface area, U is the driving voltage of the SMA wire (31), m is the mass, C is the specific heat capacity, and t is the time. Phase transformation kinetics sub-model: describes the relationship between martensite volume fraction ξ and temperature T and stress σ, and the volume fraction of detwinned martensite during heating. satisfy: ； in, To determine the volume fraction of twinned martensite, , Here, σ represents the start and end temperatures of the austenitic phase transformation, and σ is the stress. The equivalent conversion factor for austenitic phase transformation stress; Resistance-strain quantum model: describing the resistance R and strain of the SMA wire (31) The resistance R of the SMA wire (31) can be expressed as follows: ； in, , ξ represents the resistivity of the martensitic phase and the austenitic phase, respectively; ξ represents the volume fraction of martensite; l represents the length of the SMA wire (31); and S represents the cross-sectional area. strain The martensite volume fraction ξ satisfies: ； in, For the real-time strain of the SMA wire (31), and These are the martensitic elastic modulus and the austenitic elastic modulus, respectively. Strain-Angle Sub-model: Describes the tail rudder deflection angle With the strain of the SMA wire (31) The relationship between the tail rudder deflection angle satisfy: ； in, For the tail rudder deflection angle, For the real-time strain of the SMA wire (31), To maximize recoverable strain, This is the maximum deflection angle.

7. The tail control system of a biomimetic flapping-wing aircraft according to claim 6, characterized in that: The multiphysics coupling control unit (41) has two built-in control modes: Step control mode: The PWM duty cycle is increased or decreased in fixed steps of 1%-5% to achieve step adjustment of the tail rudder angle; Direct control mode: Based on the target tail rudder angle, the required PWM duty cycle is calculated by back-calculating the multiphysics coupling model, and the tail rudder is directly driven to deflect to the target position.

8. The tail control system of a biomimetic flapping-wing aircraft according to claim 7, characterized in that, Based on the target tail rudder angle, the required PWM duty cycle is specifically calculated using the multiphysics coupling model: Based on the target tail rudder angle, the effective voltage U required to drive the SMA wire (31) is calculated using the multiphysics coupling model. Based on the relationship between the effective voltage U and the PWM duty cycle The required PWM duty cycle is calculated, where U is the effective voltage. Where is the power supply voltage, and D is the PWM duty cycle.

9. A tail control method for a biomimetic flapping-wing aircraft, using the tail control system of a biomimetic flapping-wing aircraft as described in claim 8, characterized in that, Includes the following steps: S1. The wireless communication unit (42) receives external control commands and obtains the target tail rudder angle; S2. The microcontroller calculates the theoretical PWM duty cycle required to achieve the target tail rudder angle based on the multiphysics coupling model. The S3 and SMA wire (31) drive circuits output PWM signals with corresponding duty cycles to drive the SMA wire (31) to heat up and generate a contraction displacement, and the pulley transmission mechanism (33) drives the tail rudder to deflect. S4. The microcontroller back-calculates the current strain of the SMA wire (31) based on the resistance-strain sub-model, and then calculates the current actual deflection angle of the tail rudder through the strain-angle sub-model. S5. Compare the actual tail rudder deflection angle with the target tail rudder angle. If the deviation exceeds the set threshold, adjust the PWM duty cycle according to the deviation to achieve closed-loop control. S6. Repeat steps S3-S5 until the tail rudder deflects to the target tail rudder angle and remains stable.

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